[tbone17]

Does anyone have any experience with polyurethane motor mounts in a LT1 car? A customer brought in a 95 Trans Am that has a significant vibration at 2500 rpm the motor seems to run ok, but it has poly mounts in it, and I was wondering how smooth these cars are with these mounts in normally. Any thoughts?

This post has been edited by tbone17: Apr 20 2015, 06:49 PM

[Blainefab]

Does anyone have any experience with polyurethane motor mounts in a LT1 car? A customer brought in a 95 Trans Am that has a significant vibration at 2500 rpm the motor seems to run ok, but it has poly mounts in it, and I was wondering how smooth these cars are with these mounts in normally. Any thoughts?

I've run poly in the motor and trans - maybe a little more high frequency buzz gets into the cabin but nothing that RPM specific - I'd look elsewhere. A couple thoughts:

The OEM damper rubber can fail and start to separate
has the clutch been changed recently? OEM LT1 is externally balanced with an off balance flywheel
check the bellhousing for cracks - the upper bolt bosses can crack off
check plug wire routing from opti to plugs - swap a pair of cyls and it will run but not right

[tbone17]

Does anyone have any experience with polyurethane motor mounts in a LT1 car? A customer brought in a 95 Trans Am that has a significant vibration at 2500 rpm the motor seems to run ok, but it has poly mounts in it, and I was wondering how smooth these cars are with these mounts in normally. Any thoughts?

I've run poly in the motor and trans - maybe a little more high frequency buzz gets into the cabin but nothing that RPM specific - I'd look elsewhere. A couple thoughts:

The OEM damper rubber can fail and start to separate
has the clutch been changed recently? OEM LT1 is externally balanced with an off balance flywheel
check the bellhousing for cracks - the upper bolt bosses can crack off
check plug wire routing from opti to plugs - swap a pair of cyls and it will run but not right

Allan, can you be more specific about the clutch? I know it was changed right before this guy bought the car, what would be screwed up in there to cause a vibration?

[Blainefab]

Does anyone have any experience with polyurethane motor mounts in a LT1 car? A customer brought in a 95 Trans Am that has a significant vibration at 2500 rpm the motor seems to run ok, but it has poly mounts in it, and I was wondering how smooth these cars are with these mounts in normally. Any thoughts?

I've run poly in the motor and trans - maybe a little more high frequency buzz gets into the cabin but nothing that RPM specific - I'd look elsewhere. A couple thoughts:

The OEM damper rubber can fail and start to separate
has the clutch been changed recently? OEM LT1 is externally balanced with an off balance flywheel
check the bellhousing for cracks - the upper bolt bosses can crack off
check plug wire routing from opti to plugs - swap a pair of cyls and it will run but not right

Allan, can you be more specific about the clutch? I know it was changed right before this guy bought the car, what would be screwed up in there to cause a vibration?

It's been 10yrs or so since I dealt with a LT1 clutch, but I recall bring the old and new flywheels to a balance shop near an airport, and having the new match balanced to the old. The LT1 is externally balanced from the factory using the flywheel. When a motor is built with aftermarket parts the internals are internally balanced, and the flywheel needs to be neutral balanced. That is about the extent of my LT1 memories. Google 'lt1 clutch balance' for more info

The damper also is part of the motor balance - it needs to be nuetral balanced

This post has been edited by Blainefab: Apr 24 2015, 01:29 AM